Spillway review ordered at Bullards Bar
The Yuba County Water Agency will do a spillway analysis at Bullards Bar Reservoir after the Federal Energy Regulatory Commission requested it.
The agency this week confirmed in a letter to FERC that it would begin the inspection process next month.
FERC’s request came after problems at Oroville Dam’s spillways in February caused the evacuation of nearly 200,000 people from Butte, Sutter and Yuba counties.
Tim Truong, the agency’s chief dam safety engineer, wrote that the agency was responding to a May 23 letter
from FERC “requesting a plan and schedule to complete an assessment of New Bullards Bar Dam Spillway.”
FERC’s letter to the Water Agency wasn’t posted to the federal agency’s website.
According to Truong, the inspection will include a review of existing drawings and construction photos, use of an unmanned aerial vehicle and a field inspection.
The field inspection will include ground penetrating radar, impulse response spectrum testing and qualitative soundings, the letter said.
Last month, inspectors from FERC and state Division of Safety of Dams visited Bullards, which has a maximum capacity of about 966,000 acre-feet. An acre-foot is about 326,000 gallons.
During their June 6 meeting, agency directors were told the “inspection and findings were relatively minor and rou- tine, although both FERC and DSOD are and will continue to put more emphasis on (Bullards’) spillway,” according to the meeting minutes.
“DSOD brought a geologist, and further investigation and questions on the (Bullards’) spillway could be forthcoming.”
Directors were also told that “leakage (from the dam) has increased significantly, but cleaning of the drains in recent years and high reservoir elevation may the significant contributing factors.”
In addition, the agency will have to perform a focused probable failure modes analysis on the spillway, Truong wrote.
South Sutter Water District also will be evaluating its spillway at Camp Far West after receiving a FERC directive.